Conventionally, to close off the opening of a vehicle, whether it is an automobile, a utility vehicle, a truck, a bus or a railway carriage, a window is added, and is held in place by a connecting frame. This frame has an internal part and an external part which simultaneously grip the edges of the window glass and the aperture prepared in the body, with a seal lining.
The technique most commonly widespread for opening and closing a door window is that of making it vertically mobile in its own plane, in making it penetrate or exit the housing or the lining of the door. Panels that slide horizontally along rails formed in a frame are also known.
This technique is now commonly used and solutions to automate it are known. Providing automobiles with electrical windows is very widespread today.
This technique however has many relative drawbacks, especially with respect to problems of sealing and/or in terms of aesthetics.
Another technique has therefore been proposed by the holder of the present patent application. The principle of this technique is described in particular in the patent documents EP-0 778 168 and EP-0 857 844. The device for closing off (here below called a “flush opening” device) presented in these documents has a fixed structure and a part, or sliding panel, that is mobile relatively to this fixed unit. The mobile part is connected to the fixed unit by functional elements that provide the required mobility and are added to the face of the fixed part turned towards the interior of the vehicle.
Such a flush opening can be mounted fully independently of the vehicle and can be added from the exterior, in the housing defined for this purpose on the bodywork of the vehicle. It can also be fastened, in particular by gluing, to the lower portion of a door, according to the technique described in patent document EP-1 022 172. As such, most of the sealing problems identified hereinabove are resolved. The same approach can also be used to make roofs and especially window-fitted roofs provided with an opening.
From an aesthetic standpoint, when viewed from the exterior, the flush opening has a smooth, flush aspect due to the fact that no frame is needed on the outline of the aperture formed in the fixed unit.
In order to provide a sliding of the mobile part, which is generally constituted by a transparent panel, a guide device is provided, for example comprising a first and second guide rails mounted so as to be fixed on to the fixed unit (or fixed structure) of the opening, on either side of the aperture closed by the mobile panel. This panel is mounted on the rails to slide for example in a longitudinal direction in a plane of sliding between one (or more) positions of opening and an intermediate clearing position in which it faces the fixed panel and is cleared from it.
It will be noted that it has been envisaged to move the mobile part between the closing-off position and the intermediate clearing position, primarily according to two techniques:                a first technique for which the moving of the mobile part is a combination of a movement in a direction parallel to the plane of the fixed part and a movement in a direction perpendicular to this plane, in the form of a general swaying motion, in which the distal edge of the mobile part is, at the end of travel, in the plane of the opening (the mobile part being then “across” between the closing-off plane and the sliding plane). It is then enough to bring the proximal edge, for example manually, to provide for the closing off; and        a second technique for which the mobile part remains constantly in a plane that is substantially parallel to the plane of the fixed part during its movement.        
An embodiment of the invention relates more particularly to this second technique for closing off, its alternatives and its improvements.
The holder of the present patent application has indeed proposed an improvement in the guiding and locking of such “flush openings” described especially in the document PCT/EP2008/067264 (U.S. Publ. No. 2011/0006558), incorporated by reference in the present description.
In this approach, the flush opening comprises a fixed structure in which there is defined an opening and at least one sliding panel having a frame bearing at least one guiding peg (generally two pegs on the upper part and two pegs at the lower part). Two slides, or shuttles, fixedly joined to the pegs are provided and assembled so as to enable a relative movement of the slides with respect to a corresponding guide element along the sliding axis of the sliding panel so as to enable a movement of said sliding panel in a direction perpendicular to the plane of said fixed structure.
Thus, the sliding panel is fixedly joined directly to a guide element and to at least one slide by means of the guiding pegs, guided in a rail path of a simple, appreciably rectilinear form so as to enable it to be made mobile in the direction of the sliding axis or perpendicularly to the plane of the fixed structure.
It will be noted that the term “plane” herein is understood in a broad sense: the plane formed by the opening is sometimes curved, in one or even two directions (this also justifies in certain cases the term “substantially” used in the description and the claims).
This device therefore makes it possible to rest the sliding panel on a widened surface of the rail by means of the sliding element and the slide and to use rails of a limited thickness corresponding appreciably to the thickness of the slide or the sliding element and/or to the thickness planned for the gluing of the rail on to the fixed structure.
This interesting technique proves however to be difficult to implement on an industrial scale both for manual flush openings and for motor-driven (also called electrical) flush openings.
Indeed, the mobile panel tends to press against the rails when the actuation of the handle is not done exactly at the centre of the handle, i.e. at equal distance between the two shuttles. When the actuation is off-centered, the forces applied to each shuttle are different, thus leading to an arching of the mobile panel or even to a complete jamming of this mobile panel.
However, it is not easy to verify whether the user has made a centered actuation, especially for a handle as described in the document PCT/EP2008/067264, already referred to, that extends throughout the height of the sliding panel.
This risk of strain is reinforced by the major tolerance values dictated in the automobile field, which do not allow any fine adjustment of each opening but on the contrary require clearances of several millimeters.
In these many embodiments, it is also necessary that the guide rails of the mobile panel should not be parallel, thus adding further strain and further increasing this risk of arching.
The problem is similar in the case of electrical flush openings. The force provided to the lower shuttle, as proposed in the document PCT/EP2008/067264 risks being different from the one applied to the upper shuttle through the crossbeam, which may lead to arching and/or jamming.
Consequently, the manufacture of these openings and their integration into the vehicle are generally complex and costly.
Another drawback of this prior-art technique is that it makes it necessary, especially in a manual implementation, to have a frame and/or a handle that are relatively thick, interfering with transparency in the opening and in certain cases affecting aesthetic quality.